Multi-articulated catheters with safety methods and systems for image-guided collaborative intravascular deployment

ABSTRACT

Systems and method for controlling the bending of a robotic catheter. A control backbone of the robotic catheter is coupled to a linear movement stage by a spring and linear movement of the control backbone causes a controllable bending of the robotic catheter. A sensor monitors a deflection of the spring and the bending of the catheter is controlled based on the spring deflection signal from the sensor. The spring allows passive bending of the robotic catheter without movement of the active linear movement stage and, conversely, allows external forces applied to the robotic catheter to limit a bending movement of the robotic catheter caused by movement of the active linear movement stage. In some implementations, the robotic catheter includes a selectively deployable tip mechanism for deploying a steerable tip or for selectively exposing side windows on the catheter for increasing traction for clot removal.

RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 17/760,695, filed Mar. 15, 2022, which is the U.S. nationalstage entry, under 35 U.S.C. § 371, of International Application NumberPCT/US2020/051009, filed Sep. 16, 2020, which claims the benefit of U.S.Provisional Application No. 62/901,114, filed Sep. 16, 2019, entitled“SMART MULTI-ARTICULATED CATHETERS WITH SAFETY METHODS AND SYSTEMS FORIMAGE-GUIDED COLLABORATIVE INTRAVASCULAR DEPLOYMENT,” the entirecontents of each of which are hereby incorporated by reference.

BACKGROUND

The present invention relates to systems and devices for safety,deployment, and articulation of catheters including, for example,micro-catheters.

SUMMARY

In one embodiment, the invention provides a robotic catheter systemincluding an actuator, a sensor, and an electronic controller. Theactuator includes an active linear movement stage, a motor, and aspring. The motor is coupled to the active linear movement stage andconfigured to control linear movement of the active linear movementstage in response to a control signal. The spring couples the activelinear movement stage to a control backbone of a robotic catheter and isconfigured to transfer linear movement from the linear movement stage tothe control backbone. Linear movement of the control backbone causes acontrollable bending of the robotic catheter. The sensor is configuredto monitor a spring deflection of the spring. The electronic controlleris configured to generate a control signal to control the bending of thecatheter based at least in part on the spring deflection signal from thesensor.

In some embodiments, the spring allows a bending movement of the roboticcatheter due to an external force applied to the robotic catheterwithout movement of the active linear movement stage. Conversely, insome embodiments, the spring allows an external force applied to therobotic catheter to limit a bending movement of the robotic cathetercaused by movement of the active linear movement stage.

In some embodiments, the invention provides a system for operating anarticulating micro-catheter that uses image-guidance with severalassistive modes and with device embodiments allowing manual insertion,steering via joystick and collaborative control with virtual fixtures.In some embodiments, a virtual fixture is an assistive control lawimplemented by the system that assists the robot user in achieving acertain manipulation task such as, for example, limiting movement of arobotic device to within the boundaries of a defined virtual fixture.

In another embodiment, the invention provides a smart catheter that hasthe ability to actively steer and also to go “limp” when needed. In someembodiments, the micro-catheter includes multi-articulated segments. Inyet another embodiment, the invention provides a steerable device thatenable catheters to more easily navigate by using a deployable steerabletip. In still another embodiment, the invention provides systems andmethods for enhanced traction for removal of clots using a side window.

Some embodiments provide one or more of the following: (i) steerabledevices for intracranial intervention (stroke treatment, aneurysmtreatment, arterio-venous malformation treatment, arterio-venous fistulatreatment, tumor embolization, etc.), (ii) steerable devices forinspection of colling channels/ducts in cast parts, and (iii) steerabledevices for intravascular intervention (e.g., intracardiac ablation).

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view from two different perspectives of a catheterconfigured for active articulation and passive articulation inaccordance with one embodiment.

FIG. 2 is a schematic diagram of a system for controlling thearticulation of the catheter of FIG. 1 with a passive safety mechanism.

FIG. 3A is a perspective view of a system for operating thearticulatable catheter of FIG. 1 in use.

FIG. 3B is a perspective view of an actuator unit for the articulatablecatheter in the system of FIG. 3A.

FIG. 3C is a perspective view of a user control for the system of FIG.3A.

FIG. 3D is a perspective view of the actuator of FIG. 3B.

FIG. 4 is a block diagram of a control system for operating thearticulatable catheter in the system of FIG. 3A.

FIG. 5 is a flowchart of a method for controlling articulation of thecatheter using the system of FIG. 4 .

FIG. 6 is a flowchart of a method for controlling articulation of thecatheter in a first mode of operation (i.e., Mode 1: PassiveCompliance).

FIGS. 7A, 7B, and 7C are elevation views of the articulatable catheterdemonstrating both active and passive articulation.

FIG. 8 is a flowchart of a method for controlling articulation of thecatheter in a second mode of operation (i.e., Mode 2: ActiveCompliance).

FIG. 9 is a flowchart of a method for controlling articulation of thecatheter in a third mode of operation (i.e., Mode 3: User ControlledInsertion & Steering).

FIG. 10 is a partially transparent elevation view of a deployablecatheter with side windows for increased traction when removing a clot(or thrombus).

FIG. 11 is a flowchart of a method for operating the catheter of FIG. 10.

FIGS. 12A and 12B are partially transparent elevation views of acatheter with a selectively deployable, steerable tip in accordance withone embodiment shown with the steerable tip before and after deployment.

FIG. 13 is a partially transparent elevation view of a second example ofa catheter with a selectively deployable, steerable tip in accordancewith another embodiment.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

FIG. 1 illustrates one example of a catheter configured for both passivearticulation and active/controlled articulation where theactive/controlled articulation is provided by applying a pushing/pullingforce on a proximal end of the catheter. This particular design usesantagonistic pulling and pushing on concentric tubes with eccentricflexures to achieve a controlled bending of the catheter body. Threethin-walled, super-elastic NiTi tubes (i.e., an inner tube 101, anintermediate tube 102, and an outer tube 103) are micro-machined usingelectron discharge machining or femtosecond laser to create a series offlexures designed in a specific way to reduce flexural rigidity.

The inner tube 101 serves as a main support for the catheter and isproximally notched with bidirectionally alternating flexures 106 thatreduce its flexural rigidity so that the inner tube 101 acts as apassively bending micro-catheter in its proximal portion. The distal tipof this inner tube 101 has a different flexure pattern consistent withforming an antagonistic bending segment 104 with the intermediate tube102. The intermediate tube 102 is concentrically arranged around theinner tube 101 and fixedly coupled to the inner tube 101 at their distalends. By pushing/pulling the inner tube 101 relative to the intermediatetube 102 (e.g., pushing/pulling the inner tube 101 while theintermediate tube 102 is fixedly coupled to the base of the actuationunit), the distal bending segment 104 of the catheter is controllablybent.

The outer tube 103 is concentrically arranged around both the inner tube101 and the intermediate tube 102. The outer tube 103 in the example ofFIG. 1 has a shorter length than the inner tube 101 and the intermediatetube 102 and the distal end of the outer tube 103 is fixedly coupled tothe intermediate tube 102. Flexure patterns are formed in the outer tube103 and the portion of the intermediate tube 102 that is surrounded bythe outer tube 103 in order to provide another antagonistic bendingsegment 105 in the catheter. Similar to the operation of the distalbending segment 104, by pushing/pulling the outer tube 103 relative tothe intermediate tube 102, the proximal bending segment 105 of thecatheter is controllably bent.

In the example of FIG. 1 , the flexure patterns in the distal bendingsegment 104 and the proximal bending segment 105 are angularly offset sothat the distal tip of the catheter can be positioned in 3D space bycontrollable bending of the catheter (i.e., with twodegrees-of-freedom). Also, in the example of FIG. 1 , the alternatingflexures 106 extended further along the inner tube 101 towards theproximal end of the catheter than the proximal bending segment 105.Accordingly, in some implementations, the catheter is configured toprovide actively-controlled bending nearer to its distal tip and toprovide passive bending nearer to its proximate end.

FIG. 2 illustrates an example of a system for controlling the activebending of a catheter using series-elastic actuation. Although thesystem of FIG. 2 is described in reference to the catheter of FIG. 1 ,the series-elastic actuation functionality can also be adapted for usein other types of articulatable catheters (for example, continuum robotsin which bending of segments is controlled by pushing/pulling individual“backbones”). This series-elastic actuation provides for faulttolerance, increases safety, and allows force sensing at the cathetertip.

In the example of FIG. 2 , each controllable “backbone” of the catheter201 (i.e., the tubes, wires, etc. in the catheter to which a linearpush-pull force is applied in order to control the active bending of thecatheter) is coupled to an actuator 203 that applies a linear push/pullforce to the backbone. Each backbone of the catheter 201 iscoupled—either directly or indirectly (e.g., by a wire 205) to aprecision calibrated spring 207 that is supported on a linear ballbearing (not pictured). The opposite end of the spring 207 is coupled tothe actuator 203. In this manner, the pushing/pulling force is appliedto the backbone of the catheter 201 by the actuator 203 through thespring 207.

As discussed further below, the spring provides an additional passivesafety mechanism for unintended bending forces applied to the catheter,for example, due to contact between the catheter and an internalanatomical structure when the device is operated in a human body. Also,deflection of the spring is monitored by a controller and used as aninput for the active bending control of the catheter (as also discussedin further detail below). Although the examples described herein referprimary to a spring 207, other elastic elements might be utilized inother implementations including, for example, elastomers, programmableelectromechanical devices such as voice coil actuators, or otherelectromechanical actuators that have their own controller to make thembehave as a spring.

FIGS. 3A through 3D illustrate further details of the catheter actuatorand an example of the catheter system in use by a medical professional.As shown in FIG. 3A, a catheter insertion robot 301 is coupled to amovable cart 303 by a statically balanced arm 205. A fluoroscopicimaging system 307 is positioned to capture image data of a patient andof the catheter inserted into the patient's anatomy. Image data from thefluoroscopic imaging system 307 and other information is displayed on ascreen that can be viewed by the medical professional 309 operating thesystem. As shown in further detail in FIG. 3C, one or more user controls(e.g., a joystick 321) is positioned on the patient table in order toreceive user input commands from the medical professional 309. Althoughthe joystick 321 is shown attached to the patient bed in the example ofFIGS. 3A and 3C, the user controls may be positioned elsewhere (e.g.,attached to the movable cart 303) in other implementations.

FIG. 3C illustrates the catheter insertion robot 301 in further detail.An actuation unit 311 is coupled to the catheter 313 to apply bendingforce to the catheter 313. The actuation unit 311 is also coupled to aninsertion stage 315 configured to advance and retract the catheter 313by controllably altering a linear position of the actuator unit 311. Theinsertion stage 315 (and, thereby, the actuation unit 311) is coupled tothe distal end of the arm 305 by a quick connect interface 317 oranother type of mounting bracket.

FIG. 3D illustrates the actuation unit 311 in further detail. Theactuation unit 311 includes a catheter actuator 331 configured to applybending forces to the catheter 313 and a rotary stage 333. The rotarystage 333 is configured to controllably rotate the catheter 313 byapplying a rotating force to the catheter actuator 331. As shown in theinsert in FIG. 3D, the catheter actuator includes an active carriage 335that is coupled by a precision spring 337 to a free-floating carriage339. A backbone 440 (e.g., one of the concentric tubes in the catheterof FIG. 1 ) extends through the active carriage 335 and is fixedlycoupled to the free-floating carriage 339. To adjust the linear positionof the backbone 440, the active carriage 335 is moved linearly by amotor. The spring 337 conveys this linear movement to the free-floatingcarriage 339 which, in turn, transfers the linear movement to thebackbone 440.

The spring 337 allows for linear movement of the free-floating carriage339 and the backbone 440 that does not exactly match the linear movementof the active carriage 335. As described in further detail below, thisdifference in linear movement provides an additional passive safetymechanism for the catheter 313. The difference in linear movement (i.e.,the deflection of the spring) is also monitored and both motor-encoderfeedback & the measured spring deflection are used to deduce thejoint-level forces applied to the catheter 313 and to, in turn, controlthe active bending of the catheter 313. In the example of FIG. 3D, ahigh precision potentiometer 341 is configured to measure springdeflection by monitoring the distance between the active carriage 335and the free-floating carriage 339.

FIG. 4 illustrates an example of a control system for operating thecatheter actuator 331. A controller 401 includes an electronic processor403 and a non-transitory, computer-readable memory 405. The memory 405stores data and computer-executable instructions that are accessed andexecuted by the electronic processor 403 to provide the functionality ofthe controller 401. The controller 401 is communicatively coupled to animaging system 407 (e.g., the fluoroscopic imaging system 307 of FIG.3A), one or more spring displacement sensors 409 (e.g., thepotentiometer 341), the catheter actuator 411 (e.g., the motors of theactuation unit 311), and a user interface 413 (e.g., the display screenof the imaging system 307 and the user input controls 321). When thesystem is used in medical applications for controlling the movement ofthe catheter within a patient's body, the image data received by thecontroller 401 from the imaging system 407 may include, for example,images of the internal anatomy of the patient and image data showing thecatheter 313 positioned within the internal anatomy. However, althoughthe examples described herein are related to the medical domain, itshould be understood that there are other possible application domainswhere the systems and methods described herein might be appliedincluding, for example, the inspection of cast parts (e.g., inspectionof oil/cooling ducts in sand-cast components).

FIG. 5 illustrates an example of a method for controllably bending thecatheter using the system of FIG. 4 . In this example, image information501 from the imaging system and the measured spring deflection 503 areused as control inputs for determining the position/force to be appliedto a backbone by the actuator. Generalized force 507 is determined basedon the image information 501 and the measured spring deflection 503. Adesired heading (h_(des)) 511 is determined from image informationshowing the position of the catheter and the surrounding anatomicalstructure (e.g., from fluoroscopic image data). Based on the generalizedforce information 507 and the desired heading (h_(des)) 511, thecontroller 401 calculates a reference joint force (τ_(ref)) 509. In someimplementations, the reference joint force (τ_(ref)) 509 is calculatedusing the equation:

$\begin{matrix}{\tau_{ref} = {{k_{p}\underset{e_{h}}{\underset{︸}{\left( {h_{cur} - h_{des}} \right)}}} + {k_{i}{\int{\left( {h_{cur} - h_{des}} \right){dt}}}}}} & (1)\end{matrix}$

where h_(cur) is the current heading of the catheter tip and eh is anerror metric that captures deviation of the current catheter tip headingfrom the desired heading (h_(cur)−h_(des)).

A motor control signal (u) 513 is then determined by the controller 401based on the calculated reference joint force (τ_(ref)) 509 and themeasured spring deflection 503 using the equation:

u=k _(p)(τ_(cur)−τ_(ref))+k _(i)∫(τ_(cur)−τ_(ref))dt  (2)

where τ_(cur) is the current joint force of the catheter and isdetermined based on the known position of the actuator (e.g., from motorencoder feedback from the motor driving the active carriage 335) (K) andthe measured spring deflections (x) where τ_(cur)=Kx.

In some implementations, Equation (2) is used to implement aproportional integrator law to cause the joint forces to converge onτ_(ref). In such cases, u is the motor control signal (e.g., the currentif the motors are controlled in current mode or velocity if the motorsare controlled in a velocity mode). In some implementations, urepresents the “actuator effort” (e.g., current force) or position). Ifu is position, then it is assumed that there is a tertiary-levelposition controlled (e.g., PID position controller) for each joint.

Since the catheter will likely experience some twist from its point ofentry to its distal tipe, reliance on pre-operative path planning is notsufficient. Even though vessel anatomy does not change with the head ofthe patient fixed, the robot kinematic mapping does change and an addedsafety measure is needed to allow safe semi-automated navigation. Twotools that may be used to address this challenge include (1) a periodicJacobian update using joint-level and image segmentation information,and (2) the use of joint level force sensing for updating thejoint-level commands based on the nominal path plan. The periodicJacobian update relies on numerical estimations of input-output mappingsbetween joint motions from encoders and catheter bending from imagesegmentation. This approach may be augmented with use of joint-levelforce sensing and a static model of the catheter. If one simulates thecatheter insertion along a nominal path plan, one expects a joint forcelevel {circumflex over (τ)} for every given arc length along the path. AJacobian of this force as a function of twist angle may be obtainedthrough simulation on different twist angles while including the staticsmodel of the robot as a predictor of the joint force expected value{circumflex over (τ)}. Using a parametrization of this Jacobian (e.g.though Fourier series compression or though brute force look-up tables)one can estimate the twist angle. Finally, an ultimate safety check willbe applied if the difference between {circumflex over (τ)} and τ_(cur)exceeds a threshold. This would be in the form of pausing insertion,applying a relaxation of joint forces through an active compliance lawwhere τ_(ref) is set to {circumflex over (τ)} based on imagesegmentation data feeding into the statics model of the catheter. Oncethe error in joint level force is minimized within a threshold zone,automatic insertion may proceed with a correction term for τ_(ref) basedon the output of the compliance control law.

Based on the general control mechanism illustrated in FIG. 5 , thesystem in some implementations is configured to operate in threedifferent control modes: Mode 1—Passive Compliance (FIG. 6 ), Mode2—Active Compliance (FIG. 8 ), and Mode 3—User Steering (FIG. 9 ).

FIG. 6 illustrates an example of a method for implementing operation ofthe actuator system under Mode 1—Passive Compliance. In someimplementations, this mode is used during the stage of manual insertionof the catheter tip. During this phase, the actuation unit is put in thepassive compliance mode to protect the catheter tip from over-loading ofits backbones. The motor control signal u is calculated (step 605) usingthe control law of Equation (2) based on the measured spring deflection603 and with τ_(ref)=0 to allow the actuation unit to comply withdisturbances due to the medical professional manually manipulating thecatheter body.

FIGS. 7A, 7B, and 7C illustrate an example of the problems involved withmanual insertion of a robotic catheter that are addressed by the Mode 1operation of FIG. 6 . FIG. 7A shows a catheter 701 with an activelyarticulatable segment 703 and a passively articulatable segment 705.Again, although the example of FIG. 7A shows only one bending segment,it should be understood that the catheter 701 in other implementationsmay have multiple actively bending segments being actuated by wires orother means of mechanical actuation. FIG. 7B shows the same catheter 701with the active segment 703 deflected due to an external load (appliedby a push/pull force on backbones 707) while the passive segment 705remains straight. However, in some implementations, the bending angle atthe distal tip of the catheter does not depend on the shape of theactuated segment (i.e., if it is deflected under loading its tip willmaintain its angle). In some such implementations, this phenomenon isdue to circumferential placement of the actuation wires 707.

During manipulation by a medical professional, the passive segment 705is likely to be bent. As shown in FIG. 7C, if an actuator such asillustrated in FIG. 3D is used to control the bending of the activesegment, then bending of the passive segment 705 causes a correspondingbending of the active segment 703. In contrast, Mode 1 operation adjuststhe actuation force applied to the backbones 707 by the actuator toenable the passive segment 705 to bend without causing a correspondingbending of the active segment 703. Accordingly, Mode 1 operation allowsthe catheter to “go limp” during insertion.

Also, in some implementations, Mode 1 operation allows deployment in anon-calibrated setting where, after deployment, a user can toggle Mode 1to relax any internal forces in the system due to model discrepancy andlack of exact registration between the robot and the environment. Insome implementations, Modes 2 & 3 (discussed below) may also allowperiodic toggling into Mode 1 to address discrepancies in the model dueto cumulative registration error. Such toggling will occur based on astate estimator or based on thresholding on spring deflection fromexpected values based on image segmentation of the catheter tip.

FIG. 8 illustrates an example of a method for implementing operation ofthe actuator system under Mode 2—Active Compliance. During Mode 2operation, the user provides input commands 801 to control the insertion807 of the catheter while the device actively complies with thesurrounding environment and controls steering of the catheter tip.Accordingly, Mode 2 operation may be used, for example, duringuser-commanded insertion and feeding of the catheter in non-bifurcatedsegments of the vasculature. In this mode, the reference force τ_(ref)815 is changed as a function of a desired heading h_(des) 813 (i.e., adesired tip orientation) that will be determined based on an estimatedgeneralized force 811 and a theoretical generalized force 809 determinedbased on a static model of the catheter. The estimated generalized force811 is determined based on image information 803 from the fluoroscopicimaging system and spring deflection measurements 805.

FIG. 9 illustrates an example of a method for implementing operation ofthe actuator system under Mode 3—User Controlled Insertion/Steering. Insome implementations, Mode 3 operation is initiated in response to auser override command. The user can choose to use a user control input(e.g., joystick 321) to drive the robot while observing the standardbi-plane fluoroscopy display (e.g., image data shown in the display ofthe imaging system 307 in FIG. 3A). In this mode, several backgroundprocesses will run to ensure safety of the operation. A local virtualfixture law will be used to filter user commands and to determine acommanded increment of insertion depth change & an increment of changein catheter tip heading. A safety metric based on a calibrated model ofthe catheter and based on measurements is used to trigger a mode switchin the event of an unsafe condition being detected due, for example, toerroneous commands and/or misregistration. In some implementations, inresponse to detecting an unsafe condition, the system will display anotice to the user (e.g., on the display screen of the imaging system307 of FIG. 3A) and prompt the user to elect to toggle to either Mode 1or Mode 2. In other implementations, the system will automaticallytoggle to Mode 1 until convergence and then the system will revert backto Mode 3 operation. However, if after repeated toggles to Mode 1, anunsafe condition is detected, the user will be advised to toggle intoMode 2 to allow safe retraction of the catheter.

As shown in FIG. 9 , the inputs used to control operation of thecatheter during Mode 3 operation include user command inputs 901, imageinformation 903 (e.g., from the fluoroscopic imaging system), measuredspring deflection 905, and a pre-operative 3D model of the vasculature907. The controller 401 is configured to define one or more localvirtual fixtures 911 based on the user commands, image information, andthe pre-operative 3D model. The virtual fixtures 911 define limits onthe direction/distance which the catheter can be moved. Additionally, asin Mode 2 operation, the controller 401 will also determine atheoretical generalized force 913 based on a static model of thecatheter and the pre-operative 3D model 907 of the vasculature. Anestimated generalized force 915 is also determined based at least on thespring deflection measurements 905.

Based on the defined local virtual fixtures 911, the theoreticalgeneralized force 913, and the estimated generalized force 915, thecontroller 401 then calculates an estimated safety metric 917. If thesafety metric 917 indicates that further insertion or retraction of thecatheter is safe (step 919), the controller 401 transmits a controlsignal to the linear stage actuator causing it to adjust the linearinsertion depth 921. Similarly, if the safety metric 917 indicates thatthe bending movement corresponding to the user input command 901 is safe(step 923), the controller 401 updates the desired heading h_(des) 925and calculates a new reference joint force τ_(ref) which are, in turn,used to determine an updated motor control signal u 929 that istransmitted by the controller 401 to the actuator to cause it to adjustthe bending position of the catheter. However, if the safety metric 917indicates that the insertion command and/or the bending command based onthe user input command 901 is unsafe, the system displays a notice 931to the user on the graphical interface (e.g., the screen of the imagingsystem 307 in FIG. 3A) and then toggles into either Mode 1 or Mode 2operation (step 933) (either automatically or in response to a userselection).

As discussed above, in some implementations, a 3D rendering of thevasculature and the catheter is shown on the display screen during Mode3 operation along with a digital overlay of the location of a clot.However, user-controlled operation can be complicated in this situationbecause the user is interpreting the 3D images and mapping theirperception of corrective action needed for steering the catheter to aproper joystick motion command. This can be simplified in Mode 3operation by selectively filtering of “erroneous” joystick commands. Forexample, the controller 401 may be configured to appropriately filter anincremental heading change {dot over (h)}_(des)(i.e., a time derivativeof h_(des)) to help the user command the motion of the catheter onlywithin a defined plane Π (where the plane Π is defined by the currentcatheter tip heading h_(cur) and the heading of the local vasculatureh_(vasc) corresponding to the curve local tangent. Movement within thisplane would be expected to be the most desirable bending movementbecause it would produce the shortest path for closing the heading errorand would also prevent the user from having to worry about watching theensuing motion of the catheter in the two bi-plane views.

In some implementations, this is achieved by defining P_(Π) as aprojection matrix that projects vectors into Π. The user input virtualfixture can then be defined as:

{dot over (h)} _(des) =k _(p1) P _(Π) {dot over (h)} _(user) +k_(p2)(1−P _(Π)){dot over (h)} _(user)  (3)

where k_(p1) and k_(p2) are proportional scaling terms and {dot over(h)}_(user) is the incremental heading change commanded by the usercommand 901 (e.g., the user command received through the joystick 321).The first scaling term allows the user to move the catheter tip only inthe plane. The second term allows the user to move the catheter outsidethe plane. Accordingly, k_(p1)>k_(p2) in order to render assistivebehavior without locking the user into the virtual fixture plane.

In some implementations, the bi-plane fluoroscopy images displayed onthe display screen (e.g., 307 in FIG. 3A) will be augmented by thecontroller 401 with force information to the user that will be in theform of a color bar overlay and an auditory signal with varying pitch asa function of force at the tip of the robot.

In addition to or instead of the active and passive bendingfunctionality described in the examples above, in some implementations,the catheter is configured with a deployable tip to provide certainfunctionality selectively. FIG. 10 illustrates an example of one suchcatheter with a deployable tip. In this example, the catheter tip isdesigned for retrieval of clots using a mechanism for suction. FIG. 10shows the distal end of the catheter positioned within a blood vessel1001 near a clot 1003. The catheter includes a central tube 1005 and aretractable outer sleeve 1007. The central tube 1005 includes an opendistal end 1011 and a plurality of side windows 1013, 1015 formed in aside wall of the central tube 1005. The outer sleeve 1007 is selectivelyretractable to selectively expose and/or cover a desired number of sidewindows. For example, as shown in FIG. 10 , the outer sleeve 1007 hasbeen retracted enough to expose two of the side windows 1013 while stillcovering two other side windows 1015.

As described above, a suction force applied to the proximal end of thecentral tube 1005 causes the clot 1003 to be drawn towards the opendistal end 1011 of the central tube 1005. The clot material is similarlydrawn towards the exposed side windows 1013 by the applied suctionforce. Accordingly, the exposed side windows 1013 provide additionaltraction for removing the clot 1003. Furthermore, because theretractable sleeve 1007 in this example can be controlled to selectivelyexpose only a defined number of possible side windows, the tractionforce applied to the clot 1003 by the catheter can be selectively tunedby adjusting the linear position of the retractable outer sleeve 1007relative to the central tube 1005.

Additionally, in some implementations, the outer sleeve 1007 and thecentral tube 1005 are each equipped with a radio-opaque ring 1017 and1019, respectively. These rings 1017, 1019 are visible in the image datacaptured by the fluoroscopic imaging system and can be used as afeedback control for selectively exposing only the desired number ofside windows. In particular, the retracted position of the outer sleeve1007 relative to the central tube 1005 can be determined based on adistance between the radio-opaque rings 1017, 1019 in the captured imagedata. Based on the known dimensions of the central tube 1005 and theouter sleeve 1007 as well as the known position of the rings 1017, 1019thereon, the controller 401 can determine how many side windows arecurrently exposed and what further adjustment to the relative linearposition of the outer sleeve 1007 might be necessary to expose thedesired number of side windows.

Also, although the example of FIG. 10 shows a mechanism for selectivelyexposing side windows by retracting the outer sleeve 1007, othermechanism for exposing the side windows may be used in otherimplementations. For example, the catheter may be configured toselectively expose the side windows by rotation of the outer sleeve 1007relative to the central tube 1005 instead of by linear retraction. Insome such implementations, the outer sleeve 1007 will include differentsections positioned around the rotational axis of the outer sleeveconfigured to cover some, all, or none of the side windows of thecentral tube 1005. Accordingly, the number of exposed side windows canbe controlled by adjusting the rotational position of the outer sleeve1007 relative to the central tube 1005 to align with one of thedifferent sections.

FIG. 11 illustrates one example of a method for operating the catheterof FIG. 10 to remove a clot. The catheter is advanced into the bloodvessel (step 1101) while suction is applied to the proximal end of thecentral tube 1005. When the distal tip 1011 of the catheter contacts theclot 1003, the open distal tip 1011 will be covered/blocked by the clot1003 and the pressure/suction applied to the central tube 1005 willincrease. Therefore, the controller 401 monitors the applied pressureand suction (step 1103) and continues to advance the catheter into theblood vessel until the measured suction/pressure exceeds a definedthreshold (step 1105).

Once the distal tip 1101 of the catheter has made contact with the clot,outer sleeve 1007 is moved relative to the central tube 1005 to exposethe side windows (step 1107). The controller 401 continues to monitorthe position of the outer sleeve 1007 relative to the central tube 1007(step 1109) to determine when a target number of side windows have beenexposed (step 1111). Once the controller 401 has determined that thedesired number of side windows have been exposed, the catheter (i.e.,both the outer sleeve 1007 and the central tube 1005) is retracted topull the clot from the blood vessel (step 1113). In someimplementations, the catheter is retracted automatically when a definednumber of side windows have been exposed. In other implementations, amedical professional (e.g., a surgeon) makes the decision on when toinitiate retraction of the catheter.

In some implementations (e.g. to assist the surgeon in determining whento initiate retraction of the catheter), the system is configured toprovide an indication (e.g., a visual notice on a display screen)identifying a number of side windows that have been exposed and, in somesuch implementations, an indication of whether all of the exposed sidewindows are engaged with the clot material (as discussed in furtherdetail below). For example, in some implementations, the system isconfigured to monitor the internal pressure of the central tube 1005 asthe outer sleeve 1007 is retracted. When a side window is exposed andengages clot material, a relatively constant level of vacuum ismaintained within the central tube 1005. However, when side windows areexposed that no longer contact the clot material, the vacuum levelswithin the central tube 1005 will drop. In some implementations, thesystem may be configured to monitor for this type of drop in pressureeither while retracting the outer sleeve 1007 (e.g., to automaticallystop retraction of the outer sleeve 1007 or to indicate to the operatorthat the additional exposed side windows are no longer contacting theclot material) and/or while retracting the catheter to pull the clotmaterial (e.g., to determine whether traction force between the catheterand the clot material is decreasing or becoming unstable while the clotis being withdrawn).

Although the example above described “retracting” the outer sleeve 1007to expose the side windows, in some implementations, the outer sleeve1007 is retracted relative to the central tube 1005 by extending thecentral tube 1005 further into the clot 1003 while the outer sleeve 1007remains stationary. In some implementations, extending the central tube1005 further into the clot 1003 also helps ensure that clot material islocated at the side windows when they are exposed.

Furthermore, the example of FIG. 11 shows monitoring a suction/pressureto determine when the distal tip of the central tube 1005 has come intocontact with the clot. However, in some implementations, additionalthresholding is used to determine when the side windows have beenexposed (i.e., the suction/pressure will drop (at least temporarily)when a side window transitions from covered to exposed) and thecontroller 401 may be configured to use this thresholding mechanisminstead of or in addition to the radio-opaque rings in order todetermine when a desired number of side windows have been exposed. Also,in some implementations, additional thresholding is used after the sidewindows are exposed to determine when clot material has been drawn intothe side windows (i.e., the suction/pressure will increase again whenthe side windows are obstructed by clot material) and the controller 401may be configured to use this thresholding mechanism to initiate theretraction of the catheter only after the side windows establishadditional traction with the clot material.

Finally, in some implementations, actuation of the side window mechanismmay be triggered instead based on detected blood flow. In one suchimplementation, the system is configured to advance the catheter until avisible blood stream is detected at the proximal end of thecatheter—indicating that the catheter has poked through the clot. Thesystem then retracts the catheter until the blood stream stops—therebyindicating that the catheter tip has been fully engaged with the clot.The central tube 1005 is then axially locked in place and the outersleeve 1007 is retracted until the blood stream is again detected. Theouter sleeve 1007 is then advanced axially until the blood streamstops—indicating that the distal end of the sheath has engaged theproximal end of the clot. At this point the maximal number of sidewindows will be engaged with the clot for the purpose of increasingtraction and the catheter is retracted to pull the clot from the bloodvessel.

FIGS. 12A and 12B illustrates an example of another catheter device witha selectively deployable tip. In this example, an elastomeric steerabletip is selectively deployed through the distal end of the catheter. FIG.12A shows an example of a hydraulically-operated deployable tip 1201 ispositioned within a catheter tube 1203. The deployable tip 1201 includesa steerable tip 1205 which, in the example of FIG. 12A, has not beenextended beyond the distal end of the catheter tube 1203. Radio-opaquerings 1207, 1209 are coupled to the deployable tip 1201 and the cathetertube 1203 so that the position of the steerable tip 1205 can bedetermined relative to the catheter tube 1203 based on image datacaptured, for example, by the fluoroscopic imaging system (e.g, 307 inFIG. 3A).

FIG. 12B shows the steerable tip 1205 in its deployed position. In theexample of FIGS. 12A and 12B, the deployable tip 1201 is operated toextend the steerable tip 1205 beyond the distal end of the catheter tube1203 by applying hydraulic pressure to further inflate the deployabletip 1201. As shown in FIG. 12B, the steerable tip 1205 extending beyondthe distal end of the catheter tube 1202 is inflated to have a diameterthat is larger than that of the catheter tube 1202 forming a pouch 1211around the circumference of the steerable tip 1205 just beyond thedistal end of the catheter tube 1202. This pouch 1211, when inflated,hold the steerable tip 1205 in its deployed position.

As discussed above in reference to FIG. 12A, one or more radio-opaquerings or markers may be positioned on the deployable tip 1201 and/or thecatheter tube 1203 to provide a visual confirmation (e.g., via capturedx-ray image data) that the steerable tip 1205 has been properly movedinto its deployed position. In the example of FIG. 12A, there is ameasurable distance between the radio-opaque rings 1207, 1209 when thesteerable tip 1205 is retracted. However, in the example of FIG. 12B,the radio-opaque rings 1207, 1209 are coaxially aligned when thesteerable tip 1205 is deployed.

A steering mechanism is integrated into the steerable tip 1205 toprovide a controllable deflection or bending of the steerable tip 1205when deployed. In the example of FIG. 12B, the steering mechanismincludes an encapsulated bimorph actuator 1215 (e.g., a gold/polypyrolebimorph actuator) that extends into the steerable tip 1205 andcontrollably deflects from its central axis when a voltage is applied.This controlled deflection of the actuator 1215 pushes the steerable tip1205 to the side from the inside, which causes the steerable tip 1205 toact as an active guide-wire. Other types of steering mechanism can beused to bend or deflect the steerable tip 1205 in other implementations.For example, the deployable tip mechanism 1201 may include a set ofinternal bellows that are pneumatically operated to bend the deployedtip 1205 in a desired direction by adjusting the relative inflation ofthe different bellows (for two DoF operation). Alternatively, thesteering mechanism in some implementations may include one or morestrands extending from the proximal end of the catheter each with itsdistal end embedded in the elastomeric material on a different internalside location of the steerable tip 1205. Deflection of the steerable tip1205 is achieved by pushing or pulling the strands from the proximal endof the catheter.

In some implementations, a mechanical mechanism may also be provided toextend/retract the steerable tip 1205 and/or to latch the steerable tip1205 into its deployed position. For example, FIG. 12B shows a controlwire 1213 extending from the proximal end of the catheter tube 1203 tothe pouch 1211 of the deployed steerable tip 1205. In someimplementations, the distal end of the control wire 1213 is embeddedinto the elastomeric material of the steerable tip 1205 so that, whenthe proximal end of the control wire 1213 is pushed linearly towards thedistal end of the catheter tube 1203, the steerable tip 1205 is pushedbeyond the distal end of the catheter tube 1203 into its deployedposition. Furthermore, to retract the steerable tip 1205 back into thecatheter tube 1203, the control wire 1213 is pulled linearly towards theproximal end of the catheter tube 1203, which, in turn, pulls thesteerable tip 1205 back into the interior of the catheter tube 1203.Alternatively, in some implementations, the steerable tip 1205 can beretracted by applying a pulling force to a proximal end of theelastomeric material of the deployable tip 1201.

FIG. 13 illustrates an example of another mechanism for extending thesteerable tip into its deployed position. A set of serially stackedhollow beads 1301 is arranged within an elastomeric mold and are coupledto the steerable tip 1305. To deploy the steerable tip 1305, the hollowbeads 1301 are pushed from the proximal end of the catheter tube towardthe distal end. This pushing force transferred through the series ofhollow beads 1301 pushes the steerable tip beyond the distal end of thecatheter tube (as shown in FIG. 13 ). However, because the hollow beadsare not fixedly coupled to each other in the linear direction, thecatheter tube is still able to bend (passively or, in someimplementations, actively) along its length.

FIG. 13 also shows a steering mechanism 1303 extending from the proximalend of the catheter tube to the steerable tip 1305. This steeringmechanism can be extended through the hollow openings of the beads 1301and operate similar to the options discussed above in reference to FIG.12B. Also, in some implementations, the steerable tip 1305 may be lockedin its deployed position by hydraulic or pneumatic inflation and/or witha control-wire-based mechanism for latching a pouch of the deployedsteerable tip to the outer edge of the distal end of the catheter tubesuch as discussed above in reference to FIG. 12B. Finally, in someimplementations, the steerable tip 1305 and the series of hollow beads1301 can be retracted from the deployed position by applying a pullingforce from the proximal end of the catheter to a control wire (e.g.,control wire 1211 in FIG. 12B) or to the proximal end of the elastomericmaterial of the deployable tip.

Thus, in various different implementations, the invention provides,among other things, systems and methods for passive and active bendingof a catheter and selectively deployable catheter tips. Other featuresand advantages of the invention are set forth in the accompanyingclaims.

What is claimed is:
 1. A robotic catheter system comprising: an actuatorincluding an active linear movement stage, a motor coupled to the activelinear movement stage, wherein the motor is configured to control linearmovement of the active linear movement stage in response to a controlsignal, and a spring coupling the active linear movement stage to acontrol backbone of a robotic catheter such that the linear movement ofthe linear movement stage causes a linear movement of the controlbackbone, wherein the linear movement of the control backbone causes acontrollable bending of the robotic catheter; a sensor configured tomonitor a spring deflection of the spring between the control backboneand the active linear movement stage, and to output a spring deflectionsignal indicative of the spring deflection detected by the sensor; andan electronic controller configured to receive the spring deflectionsignal from the sensor, and generate the control signal to the motor tocontrol the bending of the catheter based at least in part on the springdeflection signal from the sensor.
 2. The robotic catheter system ofclaim 1, wherein the actuator further includes a free-floating linearmovement stage, wherein a proximal end of the control backbone isfixedly coupled to the free-floating linear movement stage, wherein thespring couples the active linear movement stage to the control backboneby coupling the active linear movement stage to the free-floating linearmovement stage.
 3. The robotic catheter system of claim 2, wherein thesensor includes a potentiometer coupled between the active linearmovement stage and the free-floating movement stage, and wherein thepotentiometer is configured to output the spring deflection signal basedon a distance between the active linear movement stage and thefree-floating movement stage.
 4. The robotic catheter system of claim 1,wherein deflection of the spring allows a bending movement of therobotic catheter due to an external force applied to the roboticcatheter without movement of the active linear movement stage.
 5. Therobotic catheter system of claim 1, wherein deflection of the springallows an external force applied to the robotic catheter to limit abending movement of the robotic catheter caused by movement of theactive linear movement stage.
 6. The robotic catheter system of claim 1,wherein a passive bending of the robotic catheter caused by an externalforce applied to the robotic catheter while a linear position of thecontrol backbone remains stationary causes a second correspondingbending of the robotic catheter at another location along the length ofthe robotic catheter, wherein the electronic controller is furtherconfigured to monitor the spring deflection signal to determine thepassive bending of the robotic catheter, and wherein the electroniccontroller is configured to generate the control signal by generating acontrol signal configured to adjust the linear position of the controlbackbone to prevent the second corresponding bending of the roboticcatheter.
 7. The robotic catheter system of claim 1, wherein theelectronic controller is further configured to receive image data froman imaging system, and determine a desired heading for the catheterbased on the image data, and wherein the electronic controller isconfigured to generate the control signal by generating a control signalconfigured to apply an active bending force to the robotic catheter byadjusting a linear position of the control backbone, wherein the activebending force is determined by the electronic controller to alter abending of the robotic catheter from a current heading to the desiredheading.
 8. The robotic catheter system of claim 7, further comprising:a user input control; and a linear advancement stage configured toadjust a linear position of the robotic catheter based on a linearadvancement control signal, wherein the electronic controller is furtherconfigured to receive a user control signal from the user input control,transmit the linear advancement control signal to the linear advancementstage to adjust the linear position of the robotic catheter based on theuser control signal, and control a steering of the robotic catheterbased on the image data and not based on the user control signal.
 9. Therobotic catheter system of claim 1, further comprising a user inputcontrol, wherein the electronic controller is further configured toreceive a user control signal from the user input control, determine adesired heading of the robotic catheter based on the user controlsignal, receive image data from an imaging system, wherein the imagedata indicates dimensions of an interior cavity and a position of adistal tip of the robotic catheter in the interior cavity, anddetermine, based at least in part on the image data, whether the desiredheading violates a safety metric for operation of the robotic catheter,wherein the electronic controller is configured to generate the controlsignal by generating a control signal configured to apply an activebending force to the robotic catheter based on the desired heading inresponse to determining that the desired heading does not violate thesafety metric.
 10. The robotic catheter system of claim 9, furthercomprising a linear advancement stage configured to adjust a linearposition of the robotic catheter based on a linear advancement controlsignal, wherein the electronic controller is further configured todetermine a desired insertion depth of the robotic catheter based on theuser control signal, determine, based at least in part on the imagedata, whether the desired insertion depth violates the safety metric foroperation of the robotic catheter, and transmit the linear advancementcontrol signal to move the robotic catheter to the desired insertiondepth in response to determining that the desired insertion depth doesnot violate the safety metric.
 11. The robotic catheter system of claim9, wherein the electronic controller is further configured to filter outuser control signals that indicate a desired heading that violates thesafety metric.
 12. The robotic catheter system of claim 9, wherein theelectronic controller is further configured to change to an alternativemode of operation in response to determining that the user controlsignal violates the safety metric, wherein, under the alternative modeof operation, the electronic controller is configured to automaticallycontrol a steering of the robotic catheter based on the image data andnot based on the user control signal.
 13. The robotic catheter system ofclaim 9, wherein a passive bending of the robotic catheter caused by anexternal force applied to the robotic catheter while a linear positionof the control backbone remains stationary causes a second correspondingbending of the robotic catheter at another location along the length ofthe robotic catheter, wherein the electronic controller is furtherconfigured to change to an alternative mode of operation in response todetermining that the user control signal violates the safety metric, andwherein, under the alternative mode of operation, the electroniccontroller is configured to monitor the spring deflection signal todetermine the passive bending of the robotic catheter, and generate thecontrol signal configured to adjust the linear position of the controlbackbone only to prevent the second corresponding bending of the roboticcatheter.
 14. The robotic catheter system of claim 1, wherein theelectronic controller is further configured to selectively operate in afirst mode, a second mode, and a third mode, wherein the electroniccontroller, when operating in the first mode, is configured to allowpassive bending of the robotic catheter caused by an external forceapplied to the robotic catheter and to adjust the linear position of thecontrol backbone based on the spring deflection signal only to preventadditional corresponding bending of the robotic catheter induced by thepassive bending, wherein the electronic controller, when operating inthe second mode, is configured steer the robotic catheter based on imagedata and not based on any user control signal from a user input control,and wherein the electronic controller, when operating in the third mode,is configured to steer the robotic catheter based on the user controlsignal received from the user input control.
 15. The robotic cathetersystem of claim 14, wherein the electronic controller, when operating inthe third mode, is further configured to: determine whether a desiredsteering indicated by the user control signal violates a safety metric,and transition from the third mode to either the first mode or thesecond mode in response to determining that the desired steeringviolates the safety metric.
 16. The robotic catheter system of claim 15,wherein the electronic controller, when operating in the third mode, isconfigured to transition from the third mode to either the first mode orthe second mode in response to determining that the desired steeringviolates the safety metric by display a user prompt requesting the userto select between the first mode and the second mode, transitioning intothe first mode in response to a user input selecting the first mode, andtransitioning into the second mode in response to the user inputselecting the section mode.
 17. The robotic catheter system of claim 1,further comprising the robotic catheter including a central tube with anopen distal end and a plurality of side windows formed along the lengthof the central tube, and an outer sleeve, wherein the outer sleeve iscoaxially positioned around the central tube and is movable relative tothe central tube from a first position where the side windows arecovered by the outer sleeve and a second position where the side windowsare exposed, wherein the robotic catheter system selectively applies asuction at a proximal end of the central tube and wherein the appliedsuction causes a clot material to engage the open distal end of thecentral tube and the exposed side windows.
 18. The robotic cathetersystem of claim 1, further comprising the robotic catheter including anouter tube and a selectively deployable, steerable tip, wherein thesteerable tip is formed of an elastomeric material, wherein thesteerable tip is linearly movable relative to the outer tube between anundeployed position and a deployed position, wherein the steerable tip,when in the undeployed position, is positioned entirely within the outertube, wherein the steerable tip, when in the deployed position, isextended beyond a distal end of the outer tube, and wherein thesteerable tip, when in the deployed position, includes a pouch that isinflated to a diameter the is greater than an internal diameter of theouter tube such that that linear movement of the steerable tip relativeto the outer tube in the direction of the undeployed position isrestricted by the inflated pouch.